1. Field of the Invention
The present invention relates to a curable composition for a heat conductive material, capable of forming a heat conductive elastomer of a satisfactory heat conductive property in a saturated hydrocarbon polymer cured by a hydrosilylation reaction, and the cured material.
2. Description of the Related Art
Heat conductive material with elasticity is already widely employed as a heat radiating or heat conducting spacer, for example, in electronic components such as various heaters, a temperature sensor, or semiconductor devices such as a transistor, a diode or an IC. For example, JP-A-2001-139733(Japanese Kokai Publication) discloses a composition including a heat conductive filler in a known base rubber such as silicone rubber or EPDM rubber, and a technology for achieving a high filling rate of the heat conductive filler.
Also the substance utilizing silicone rubber is well known. For example, JP-B-6-55891 (Japanese Kokoku Publication), JP-B-6-38460 (Japanese Kokoku Publication) and JP-B-7-91468 (Japanese Kokoku Publication) disclose technologies based on a combination of various heat conductive fillers and silicone rubber.
In such material intended for heat conduction, not only the heat conductivity of the material itself but also its adhesion property to a substrate are considered important. For achieving such adhesion to a substrate, an adhesion property to the surface of the substrate, an adaptability to the shape of the substrate and a deformation thereof are important. A material with elasticity is considered to be preferred, particularly for deformation. Also, it is easiest to apply the material to the substrate in a liquid form such as an adhesive material or a potting material on a position of use and then to cure such material.
On the other hand, a method of applying a heat conductive material in the form of a sheet or a tape is advantageous in productivity, and is employed more frequently. In such cases, the adhesion is secured by providing an adhesion layer or a tacking layer separately, or by developing a surface tackiness. Also in the aforementioned case of application in a liquid form followed by curing, the surface tackiness is desired, for example, in cases where a heat radiating fin or the like is adhered onto a cured material.
The heat conductive material is usually added with a heat conductive filler at a high filling rate in order to improve the heat conductivity. But such addition of the filler at a higher filling rate tends to cause the material to lose elasticity and decrease surface tackiness, whereby the adhesion property to the substrate is deteriorated.
On the other hand, the aforementioned method of providing the adhesion layer or the tacking layer at a lower filling rate is effective in lessening the influence of the filling rate on the surface property of the material, but requires a new step of forming such a layer, thereby being inferior in productivity.
JP-A-2001-302936 (Japanese Kokai Publication) discloses that a resin composition formed by adding a heat conductive filler to a substrate of a compound having a hydrolyzable silyl group, such as polyalkylene glycol or polyisobutylene, has excellent strength and adhesivity. However there is not particularly disclosed a method for controlling the adhesivity. And the method that is disclosed is associated with a drawback of inferior productivity, since the curing is based on moisture curing and requires several hours or longer for completion.